1. Technical Field
The present invention relates to electronic devices, and more particularly, to semiconductor devices suitable for use as a rectifier.
2. Related Art
Schottky diodes had been used for many years in the semiconductor industry as, for example, clamps and rectifiers. Schottky diodes are diodes that include a metal-semiconductor interface that forms a Schottky barrier. The metal-semiconductor interface generally includes a metal layer connected to a doped semiconductor layer. The Schottky barrier is formed at the junction of the metal layer and the doped semiconductor layer.
A substantial difference in barrier heights exists between the forward biased and reversed biased metal-semiconductor interface. When sufficient forward bias is applied, this barrier is essentially removed, thereby allowing electrons to freely flow from the semiconductor material into the metal.
Schottky diodes provide efficient rectification in power applications since their forward voltage drop is less than that of a PN junction diode. Moreover, these devices have fast recovery times making them particularly useful for high frequency rectification.
It is known that Schottky diodes tend to have poor reverse leakage characteristics. Attempts to improve the leakage characteristics have included the addition of a guard ring of the opposite polarity carrier to the Schottky diode structure. However, the fabrication of such a guard ring typically requires an additional masking step. Also, the guard ring takes up space such that Schottky diodes having guard rings require more surface space than Schottky diodes not having such guard rings.
Thus, it is desirable to find alternative approaches for improving the reverse leakage characteristics of Schottky diodes.